Gas-filled display panels, which have been made for many years, comprise envelopes made up of a base plate and a face plate hermetically sealed together and having a tubulation secured to the base plate. It is customary for a manufacturer to purchase the base plate, face plate, and the tubulations separately, and, during the manufacturing process, these parts are handled, washed and stored before they are assembled to form panels. During manufacture of the panel, the envelope is evacuated and filled through the tubulation secured to the base plate.
The tubulation comprises a glass tube having a flared bell portion, a small diameter tubular portion, and an intermediate necked-down portion, with the flared portion being sealed to the base plate. The tubulation is tipped off at the necked-down portion during the manufacturing process. It has been found in manufacturing such devices, and as they are handled, that the projecting tubulation is easily struck and broken. For many years and up to the time of the present invention, this problem has been tolerated in spite of the considerable cost of such breakage because human error was considered to be the basic cause of the problem and no technological solution was available. The true cause of the problem was not known, and, of course, no solution was available until the present invention was made.